Year-end Sale % OFF 
Abstract
Spatiotemporal signal transmission in the human subcortical visual pathway has not been directly demonstrated to date. To delineate this signal transmission noninvasively, we investigated the early latency components between 45 ms (P45m) and 75 ms (N75m) of visually-evoked neuromagnetic fields (VEFs). Four healthy volunteers participated in this study. Hemi-visual field light flash stimuli were delivered a total of 1200 times. Neuromagnetic responses were measured with a 160-channel whole-head gradiometer. In three participants, averaged waveforms indicated a subtle but distinct component that peaked with a very early latency at 44.7 ± 2.1 ms with an initial rise latency of 36.8 ± 3.1 ms, followed by a typical prominent cortical component at 75 ms. The moving equivalent current dipoles continuously estimated from P45m to N75m were first localized in the vicinity of the contralateral lateral geniculate body, then rapidly propagated along the optic radiation and finally terminated in the contralateral calcarine fissure. This result indicates that the source of P45m is the lateral geniculate body and that the early latency components P45m–N75m of the VEFs reflect neural transmission in the optic radiation. This is the first report to noninvasively demonstrate the neurophysiological transmission of visual information through the optic radiation.
Highlights
Visual evoked responses are a useful tool for evaluating visual function and are used to detect visual disturbances in clinical practice
We hypothesized that the spatiotemporal distribution of the subtle current sources in the subcortical visual pathway that are activated by visual stimulation can be detected by MEG if the type, times and frequency of the visual stimuli are appropriate
The moving equivalent current dipoles (ECDs) continuously estimated from P45m to N75m were localized in a C-shaped coloured curve in the axial plane of the magnetic resonance imaging (MRI) (Fig. 2b bottom), which, at first, was in the vicinity of the contralateral lateral geniculate body, rapidly moved along the optic radiation, reached the contralateral calcarine fissure at approximately 60 ms after the visual stimuli and remained there until 75 ms
Summary
Visual evoked responses are a useful tool for evaluating visual function and are used to detect visual disturbances in clinical practice. Visual evoked responses that are detected using magnetoencephalography (MEG) are called visual evoked magnetic fields (VEFs), which typically have several peaks at 75 ms, 100 ms and 145 ms after the presentation of visual stimuli. The spatial localization of visual cortical function can be more precisely assessed with VEFs than with VEPs. VEFs have early components in response to flash stimuli with a latency ranging from 42 to 100 ms[7, 8, 13,14,15,16,17,18,19]. To visually delineate the spatiotemporal signal transmission in the human subcortical visual pathway noninvasively, we investigated the early latency components of neuromagnetic visual responses. The number of participants is limited, this report is the first to demonstrate the functional visualization of the visual pathway
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
